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Tape Wound Core Catalog

Transformer Lamination Catalog

Cut Core Design Manual



The magnetic materials used for tape wound cores can be classified in two broad categories: (1) "Square Loop" or (2) "Round Loop". This classification is made to the relative shape of the B-H loop.

1. Square loop versions tend to have:

      1. Higher maximum flux capabilities (Bm)
      2. Wider loops (greater Hc loop width at zero flux)
      3. Higher squareness ratios (Br/Bm) - ratio of residual flux density to maximum flux density
      4. Higher core losses

2. Round loop versions tend to have:

    1. Lower Bm
    2. Narrower loops
    3. Lower squareness ratios
    4. Higher initial permeability
    5. Lower core losses

The specific characteristics of each available material are detailed on the following pages. A composite of the square B-H loops is shown in Figure 12 while Figuer 13 (see page 26) shows a composite of the round B-H loops. Preliminary design considerations plus the comparison curves and charts will enable the designer to select the optimum material for his application, and then use the detailed characteristics for final design.

Square Loop Materials
See Table II, Page 9, for comparison of specific characteristics.
Super Square 80 - 80% Ni/Fe/Mo, Super Square 80 offers the designer a magnetic material of unusual uniformity. In comparison to Square 80 (or any of its equivalents) Super Square 80 offers higher maximum flux density, higher gain and a higher squareness ration with only a very slight increase in coercive force. One noteworthy feature of this material is the remarkable uniformity of the cores produced. These cores have half the spread of typical magnetic electrical characteristics normally encountered with Square 80. This material is made to provide a high degree of thermal stability for certain magnetic characteristics like Bm/Br, H, δH. When thermal stability is a requirement, complete specifications should be reviewed with Magnetic Metals' engineering department.

Square 80 - 80% Ni/Fe/Mo-is a low coercive force material with similar characteristics to supermalloy. It offers good squareness and high gain. Core losses are quite low. Applications include low power, high efficiency inverter transformers, low level and high frequency magnetic amplifiers, magnetic modulators and pulse transformers.

Square 50 - 50% Ni/Fe/ alloy, (grain oriented). It offers the highest squareness ratio (lowest saturated reactance) and very high gain. This material has Bm while cores losses are low enough to consider its use in higher frequency applications than the silicon steels. Applications include bi-stable switching devices, inverter transformers, high performance power magnetic amplifiers, linear current transformers, timing devices, driver transformers, and wherever an extremely square loop material, manufactured to close tolerance, is required.

Microsil - 3% Si/Fe - Oriented Silicon Iron Alloy. This material is generally used for high power, relatively low frequency applications in high performance power transformers, saturable reactors, inverter transformers, magnetic amplifiers (power), current transformers, output transformers, etc. This is the least expensive of the square loop materials and has high maximum flux. The Squareness ratio is lower than for Square 50. The core losses are higher while gain is significantly lower.

Supermendur - 49% Co/49% Fe/V. This is the highest flux density material available in tape wound cores. Applications include power transformers, power magnetic amplifiers, inverters, and wherever size and weight are a major design consideration.

Round Loop Materials
See Table II, Page 9, for comparison of specific characteristics.

Supermalloy - 80% Ni/Fe/Mo. This is an 80% nickel-iron alloy processed for exceptionally high initial permeability. Applications include very low level signal transformers, low level magnetic preamplifiers, high value inductors which have no superimposed direct currents and precision current transformers.

SuperPerm 80 - 80% Ni/Fe/Mo. This is similar to Supermalloy, but it is processed for pulse and high frequency performance. Applications include very low level signal transformers, low level and high frequency magnetic preamplifiers, and high value inductors at high frequency.

SuperPerm 49 - 50% Ni/Fe/ Alloy. This material has characteristics that fall between Silicon Steel and 80% Ni/Fe/Mo. It provides the designer with high initial permeability as well as a high maximum flux. Applications include current transformers, proportioning reactors, high quality and wide frequency response transformers and medium power magnetic amplifiers.